Well for starters, 12.5 mg is a very low dose. Still, when do you take your Toprol? If you take it in the evening, then you may see very little "slow down" from Toprol by the time breakfast rolls around. You also mention "yesterday" was that breakfast or another meal?
What is your normal (past and present) resting HR? Keep in mind a rest HR of 80 isn't an alarmingly high rate, 60 may be better, but still no big problem, I believe, to have one at 80.